Cross-validation of the WAIS-IV Similarities incidental learning task.

Area of Science:

• Neuropsychology
• Cognitive Assessment
• Psychometrics

Background:

• The Incidental Learning Index based on the Similarities subtest (IL-Sim) of the Wechsler Adult Intelligence Scale-Fourth Edition (WAIS-IV) is a potential screening tool for memory deficits.
• Existing screening measures for memory impairment require rigorous validation of their reliability and diagnostic accuracy.

Purpose of the Study:

• To evaluate the reliability, convergent validity, and divergent validity of the IL-Sim index.
• To assess the IL-Sim index's effectiveness in classifying individuals with mild to severe memory impairment.

Main Methods:

• One hundred fifty-three Veterans completed the WAIS-IV Similarities subtest and the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS).
• Statistical analyses included internal consistency (Cronbach's alpha), correlational analyses with RBANS indices, and receiver operating characteristic (ROC) curve analyses (AUC) to assess discriminative ability.
• Logistic regression was used to generate probabilities of impairment across different base rates and age groups.

Main Results:

• The IL-Sim index demonstrated acceptable internal consistency (Cronbach's α = .85).
• IL-Sim showed significant correlations with memory indices of the RBANS, particularly Delayed Memory (r = .69) and Immediate Memory (r = .59), and weaker correlations with non-memory indices (rs = .26–.38), supporting convergent and divergent validity.
• The IL-Sim index exhibited excellent discriminability between individuals without memory impairment and those with at least mild or severe impairment across age groups (AUC = .83–.87).

Conclusions:

• The IL-Sim index possesses strong psychometric properties, including good reliability and validity, for assessing memory function.
• IL-Sim effectively discriminates across the spectrum of memory impairment, proving its utility as an efficient screening measure.
• The study provides practical tools (logistic regression-derived probabilities) to aid in the interpretation of IL-Sim scores for clinical use.